Many behaviors are disturbed after removal of the amygdala in adults, but it has been suggested that these functions may be almost completely spared if amygdalectomy occurs during infancy. However, previous studies of this sparing effect in monkeys have looked at only a fraction of the behaviors disrupted after adult surgery, and have not maintained the animals long enough to evaluate possible effects upon adult behavior. The proposed research will determine the amount of sparing, if any, that can be detected on several behaviors after early amygdalectomized monkeys become adults. Mature early and late operated monkeys are already available. Some tests have been completed, but require the histological work supported in this proposal before publication. In these tests, individual and social behaviors of adult early-operated and normal control monkeys were compared. The controls then were amygdalectomized, and observations of both groups were repeated. Monkeys operated during infancy could not be distinguished from monkeys operated as adults; both groups were hyperactive, socially submissive, and retarded in their habituation to environmental changes. Other tests demonstrated that early operated monkeys aso were deficient in active avoidance, but it was not clear whether this deficit was as severe as that resulting from adult surgery. Proposed tests will involve training an additional unoperated control group on the learning problems previously administered the experimental animals, after which all three groups will be trained on reversal learning set and delayed alternation problems, both of which are disrupted by adult amygdalectomy. The amount of recovery after early surgery will be evaluated by comparing early operated monkeys with those in the two other groups.